ATI 6.12.4 on ultraSparc runs slow

[Michel Dänzer]

On Die, 2010-03-23 at 23:31 +0100, jean-francois simon wrote:
> Hi,
> thanks to the people who provided support for big endian
> architectures, we are able to run the 6.12.4 ATI driver on a
> openSolaris sparc platform (T2000 niagara). the graphic is a PCIe card
> using a e4690. i can see that  the atombios works fine, it seems, and
> edid is read OK,...and the gnome desktop is functional and looks good.
> plse note that  the configuration uses shadowfb. and i have configured
> the ATI driver with 
> 
> --disable-dri
> --disable-exa
> 
> BUT, i can see that in the same conditions (same ATI driver version
> and configuration, same GPU, shadowfb being used) a linux/x86-64  box
> runs much faster:
> 
> -x11perf gives much better numbers
> -youtube videos runs smoothly, where they run  very slow/choppy on
> ultrasparc/solaris. 
> 
> also i am seeing that the ATI driver is being called on a regular
> basis (RADEONBlocHandler() ) while a flash video is being played. this
> function along with some cursor related functions (when mouse is
> moved) seem to be the only code in the ATI driver that is involved
> after X is initialized.
> 
> so i am assuming that most of the work is done by some X server
> "painting code" to the shadowfb in system ram, which is then DMA'ed to
> the scan out buffer in the GPU VRAM.

It's only DMA'ed if you implemented that. ;)

> since i see a big difference between solaris/sparc and linux/x86-64,
> one idea that comes to mind is that there could some overhead due to
> the difference in endianess between the solaris and the linux box.

I don't think that matters here, we can use GPU facilities to handle
endianness for direct CPU access to the framebuffer.

Have you tried profiling the X server in both setups to see where the
cycles are being spent in each case? I'd guess that maybe the x86 CPU is
faster and/or has higher write throughput to VRAM, e.g. due to write
combining.


-- 
Earthling Michel Dänzer           |                http://www.vmware.com
Libre software enthusiast         |          Debian, X and DRI developer